Converging Split-Flow Microchannel Evaporator to Reduce Pressure Drop
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Solution Overview
Problem
Microchannel heat exchangers face high pressure drops due to small hydraulic diameters, leading to increased energy consumption and reduced heat removal capacity in pumped systems, and potential dry-out in natural-convection or capillary-driven systems, especially when dealing with high-heat flux applications like electronic devices.
Innovation Solution
A converging split-flow microchannel evaporator design with inlet restrictions and a centrally located fluid outlet, which splits coolant flows into multiple microchannels, reducing pressure drops and stabilizing boiling flows by avoiding Ledinegg effects, thereby enhancing thermal performance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If microchannel dimensions are used to enhance thermal performance, then heat transfer coefficient is improved, but pressure drop increases
Solution Approach 1:
The flow path is divided into multiple parallel microchannels with a centrally located outlet, creating symmetric flow segments that reduce the effective flow length and pressure drop while maintaining high heat transfer coefficients through microchannel dimensions
Solution Approach 2:
The evaporator employs an asymmetric flow distribution pattern where coolant enters through peripheral inlet ports and converges toward a central outlet, creating non-uniform flow velocities that optimize heat transfer while managing pressure drop characteristics
2Temperature
If microchannel dimensions are used to enhance thermal performance, then heat transfer efficiency is improved, but energy consumption increases
Solution Approach 1:
The microchannel evaporator is segmented into multiple parallel flow paths with a central outlet, reducing the overall flow length and pressure drop, thereby decreasing the pumping power required to maintain effective coolant flow while preserving high heat transfer efficiency
Solution Approach 2:
Instead of the conventional single inlet to single outlet configuration, the design inverts the flow pattern by having multiple inlet ports distributed around the periphery and a central outlet, which shortens the effective flow path and reduces pressure drop, thereby lowering energy consumption while maintaining thermal performance
3Use of energy by moving object
If flow is driven by natural convection or capillary action, then pumping power is reduced, but flow rate decreases
Solution Approach 1:
The evaporator is divided into multiple parallel microchannel segments with a centrally located outlet, which reduces the flow path length and pressure drop in each segment, enabling natural convection or capillary-driven flow to achieve sufficient coolant flow rates without requiring external pumping power
4Stress or pressure
If flow path is divided into shorter segments, then pressure drop is reduced, but device complexity increases
Solution Approach 1:
Multiple microchannel flow segments are merged into a single centrally located outlet manifold, which collects coolant from all segments and exits through one point, thereby reducing pressure drop while avoiding the complexity of multiple separate outlets and maintaining a compact structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves improved and stable thermal performance by reducing pressure drops and flow instabilities, allowing for efficient heat removal from high-flux heat sources with reduced energy consumption and preventing dry-out, while maintaining uniform boiling flows.
Implementation Method 1
The flow of coolant liquid fed to the fluid heat exchanger may be driven by a pump, or by natural convection due to density differences and/or elevation between the incoming and exiting fluid (e.g. thermosyphons), or by capillary action in the internal passages of the exchanger
Implementation Method 2
Evaporator-type exchangers rely on the boiling mode, and have the advantages of higher heat transfer coefficients (better heat transfer) per unit of fluid flow rate of the coolant fluid. They also require much less coolant flow, as the majority of the heat is absorbed through via the latent heat of vaporization of the boiling fluid
Implementation Method 3
The fluid heat exchangers dissipate heat by thermally conducting the heat into internal passages of the exchanger, through which a coolant fluid flows, absorbing the heat conducted across the walls of the exchanger
Data Source
AI summary
In one general aspect, a converging split-flow microchannel evaporator is disclosed. It includes a conductive contact surface to mate to a surface to be cooled, with a core mounted in thermal connection with the conductive surface that defines at least one layer of microchannels. Within the core, one inlet restriction restricts the flow into each microchannel in a first group of the microchannels, and another restricts the flow into each microchannel in a second group. A centrally located fluid outlet receives the flows from opposite ends of the microchannels in the two groups. A check valve can be provided to help ensure ready startup without reverse flow.